U.S. patent number 5,155,946 [Application Number 07/729,320] was granted by the patent office on 1992-10-20 for method and apparatus for producing a water/abrasive mixture for cutting and cleaning objects and for the precise removal of material.
This patent grant is currently assigned to GKSS Forschungszentrum Geesthacht GmbH. Invention is credited to Hannes Domann.
United States Patent |
5,155,946 |
Domann |
October 20, 1992 |
Method and apparatus for producing a water/abrasive mixture for
cutting and cleaning objects and for the precise removal of
material
Abstract
A method and apparatus for producing a water/abrasive mixture
for cutting and cleaning objects and for the precise removal of
material. In a mixing chamber, an abrasive is introduced into a jet
of water that is under high pressure and passes through the mixing
chamber from an inlet to an outlet thereof. The abrasive is
conveyed directly and precisely into the water jet in the mixing
chamber along the shortest path.
Inventors: |
Domann; Hannes (Geesthact,
DE) |
Assignee: |
GKSS Forschungszentrum Geesthacht
GmbH (Geesthacht, DE)
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Family
ID: |
27198776 |
Appl.
No.: |
07/729,320 |
Filed: |
July 12, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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458784 |
Dec 29, 1989 |
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Foreign Application Priority Data
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Dec 30, 1988 [DE] |
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3844344 |
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Current U.S.
Class: |
451/75; 239/428;
239/434; 451/102 |
Current CPC
Class: |
B24C
1/045 (20130101); B24C 5/04 (20130101) |
Current International
Class: |
B24C
5/04 (20060101); B24C 5/00 (20060101); B24C
1/04 (20060101); B24C 1/00 (20060101); B24C
003/00 () |
Field of
Search: |
;51/410,427,439
;239/428,431,434,434.5,438,456 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Smith; James G.
Attorney, Agent or Firm: Robert W. Becker &
Associates
Claims
What I claim is:
1. A method of producing a water/abrasive mixture for cutting and
cleaning objects and surfaces and for the precise removal of
material, said method comprising the steps of:
introducing an abrasive, in a mixing chamber, into a jet of water
that is under high pressure and passes through said mixing chamber
from an inlet to an outlet thereof; and
conveying said abrasive directly and precisely to said jet of water
in said mixing chamber in a pressure range of from greater than 1
to not more than 120 bar.
2. A method according to claim 1, which includes the step of
conveying said abrasive into said mixing chamber in such a way that
abrasive collects about said outlet while forming an abrasive
channel, with said abrasive being deposited on all walls of said
mixing chamber.
3. A method according to claim 1, in which said abrasive is
conveyed to said jet of water at essentially right angles to an
axis of said jet of water.
4. An apparatus for producing a water/abrasive mixture for cutting
and cleaning objects and surfaces and for the precise removal of
material, said apparatus comprising:
a mixing chamber having a first inlet for receiving a high pressure
jet of water, an outlet for the discharge of said water jet after
passage thereof through said mixing chamber along a water jet axis,
and a second inlet for supplying said abrasive to said jet of
water; with said second abrasive inlet of said mixing chamber
having a central axis that extends essentially perpendicularly to
said axis of said water jet in said mixing chamber, with said
mixing chamber having an essentially cylindrical cross-sectional
configuration, and with said water jet axis forming a central axis
of said cylinder, which has a diameter that is greater than a free
path length of said water jet through said mixing chamber.
5. An apparatus according to claim 4, in which said mixing chamber
has a funnel-shaped configuration about said outlet thereof.
6. An apparatus according to claim 4, which includes a nozzle for
the discharge of said water/abrasive mixture from said apparatus,
with said discharge nozzle projecting at least partially into said
mixing chamber and providing said outlet thereof.
7. An apparatus according to claim 6, in which said discharge
nozzle is centrally disposed in said cylindrical mixing
chamber.
8. An apparatus according to claim 6, in which said discharge
nozzle is made of hard material.
9. An apparatus according to claim 6, in which said discharge
nozzle is segmented into several parts.
10. An apparatus according to claim 6, in which said discharge
nozzle, on a side facing said mixing chamber, has a funnel-shaped
configuration that widens in the direction toward said mixing
chamber.
11. An apparatus according to claim 6, in which said discharge
nozzle, on a side facing said mixing chamber, has an inlet bore
that enlarges a nozzle opening thereof.
12. An apparatus according to claim 6, which includes means for
adjusting the free path length spacing between said first inlet and
said outlet for said water jet in said mixing chamber.
13. An apparatus according to claim 12, in which said adjusting
means comprises means for shifting said discharge nozzle and/or
shifting a holder for a nozzle insert at which said first inlet of
said mixing chamber is disposed.
14. An apparatus according to claim 12, in which said adjusting
means comprises means for securing said discharge nozzle and/or
said holder within a mixing chamber body.
15. An apparatus according to claim 4, which includes means for
varying the cross-sectional configuration of said second abrasive
inlet.
16. An apparatus according to claim 15, in which said means
comprises sleeves having throughbores of various diameters.
17. An apparatus according to claim 15, which includes a plurality
of second abrasive inlets that are directed into said mixing
chamber.
18. An apparatus according to claim 4, which includes: a discharge
nozzle means provided with said outlet for said mixing chamber, and
precision cylindrical and/or conical fitting elements for centering
said discharge nozzle means relative to said water jet axis.
Description
BACKGROUND OF THE INVENTION
This application is a continuation-in-part application of
application Ser. No. 458,784, filed Dec. 29, 1989.
The present invention relates to a method and apparatus for
producing a water/abrasive mixture for cutting and cleaning
surfaces or objects and for the precise removal of material, by
introducing an abrasive, in a mixing chamber, into a jet of water
that is under high pressure and that passes through the mixing
chamber from an inlet to an outlet thereof.
Methods of this general type are known where particles of hard
material (abrasive) are added to high pressure water jets to
produce a mixture for cleaning and cutting surfaces or objects. The
advantage of using such water/abrasive mixtures rather than
utilizing a thermal process for cutting objects is that the cutting
location remains practically cold, which is of particular advantage
when using the process for cutting or cleaning objects that are
sensitive to heat. Water/abrasive mixtures are also very suitable
for cutting and cleaning or for the removal of material in
underwater applications.
With one known method of the aforementioned general type (U.S. Pat.
No. 4,648,215, Hashish et al, issued Mar. 10, 1987), abrasive is
added to a water jet that passes through a mixing chamber of an
apparatus for cutting and cleaning via a water/abrasive mixture. In
particular, the abrasive is supplied at an acute angle relative to
the water jet. The diameter of the mixing chamber is less than the
free length of the jet in the chamber.
This known supply technique results in the considerable drawback
that after a short period of use, pits or cavities form in the wall
of the mixing chamber on that side opposite the abrasive nozzle;
these cavities rapidly become very large. As a result of the
formation of these disadvantageous cavities, the known apparatus,
already after a relatively short period of use, can no longer
operate as designed.
Pursuant to the known apparatus of the aforementioned U.S. Pat. No.
4,648,215, an attempt was made to check this phenomenon by
providing at least that lower portion of the mixing chamber where
the outlet is provided with a hard metal lining that on the one
hand has the drawback that it considerably increases the cost of
producing such an apparatus, and on the other hand also leads to
erosion effects in the abrasive introduction nozzle that is
directed into the mixing chamber due to the fact that the lining
scatters abrasive back. This caused considerable wear of the
nozzle, so that tests under actual conditions of use showed that
this known apparatus, and the method carried out therewith, fell
short of expectations.
It is therefore an object of the present invention to provide a
method and apparatus for improving the effectiveness of the mixing
process in the mixing chamber, of increasing the output (hydraulic
capacity), and increasing the service life of the mixing chamber
and of the discharge nozzle.
BRIEF DESCRIPTION OF THE DRAWINGS
This object, and other objects and advantages of the present
invention, will appear more clearly from the following
specification in conjunction with the accompanying schematic
drawings, in which:
FIG. 1 is a cross-sectional view of one exemplary embodiment of the
inventive apparatus showing a mixing chamber as well as a discharge
nozzle that is disposed in the apparatus and a jet of water that
passes through the mixing chamber;
FIG. 1a is an enlarged view of the discharge nozzle of FIG. 1;
FIG. 2 is an enlarged cross-sectional view showing a nozzle insert
that includes the discharge nozzle of the water jet for entry into
the mixing chamber;
FIG. 3 is an enlarged schematic cross-sectional view showing the
region of the mixing chamber with abrasive being blown therein,
with a portion of the mixing chamber being even further
enlarged;
FIG. 4 is a cross-sectional view through the mixing chamber of FIG.
3 taken along the line 4--4, with a portion of the mixing chamber
being even further enlarged;
FIG. 5 is a partially cross-sectioned view of another exemplary
embodiment of the inventive apparatus;
FIG. 5a shows an enlarged view of the discharge nozzle of FIG.
5;
FIG. 6 shows an embodiment having two abrasive inlets;
FIG. 7 shows in a schematic representation the arrangement of four
abrasive inlets within the mixing chamber; and
FIG. 8 shows in a schematic representation the arrangement of
abrasive inlets at varying heights of the mixing chamber.
SUMMARY OF THE INVENTION
The method of the present invention is characterized primarily in
that the abrasive is conveyed directly and precisely into the water
jet that passes through the mixing chamber.
The advantage of the inventive method is that, in contrast to the
known state of the art where only a small portion of the abrasive
enters the water jet directly and the greatest portion of the
abrasive passes into the conical lower portion of the mixing
chamber where first an orientation of the path of the individual
particles of the abrasive is effected in the direction of the axis
of the water jet before the particles of the abrasive are jetted by
the spray fraction of the water jet into the directly adjoining
nozzle funnel of the discharge nozzle, with the present invention,
the particles of the abrasive, long before they reach the outlet,
i.e. pass into the inlet opening of the discharge nozzle, are
accelerated, in other words, the free length of the stream of the
water jet in the mixing chamber can be fully utilized to transfer
energy since the particles of the abrasive are blown along the
shortest path into the water jet that passes through the mixing
chamber.
A further advantage of the inventive method is the ability to
realize small free stream or jet lengths in the mixing chamber. The
slight divergence of the stream that results therefrom during entry
of the water/abrasive mixture into the inlet opening of the
abrasive nozzle causes less wear in a discharge nozzle and smaller
power losses during focusing of the abrasive jet in the discharge
nozzle.
Pursuant to one advantageous specific embodiment of the inventive
method, the abrasive is conveyed into the mixing chamber in such a
way that the abrasive also collects about the outlet while forming
an abrasive channel, with the formation of the channel being
automatically effected within the first seconds in the mixture that
is deposited about the outlet immediately after start up, which
mixture comprises the spray fraction of the water jet and the
supplied dry abrasive. The tapering of the abrasive channel about
the water jet in the mixing chamber effects an increase of the air
speed in this region and hence additionally accelerates the hard
material particles. In addition, the wall of the mixing chamber is
protected from erosion by the abrasive itself, which with the
aforementioned known apparatus very rapidly makes the apparatus
unusable.
The abrasive can also preferably be conveyed into the mixing
chamber in such a way that it is deposited on all of the walls of
the mixing chamber, thereby reliably protecting these walls from
damage due to erosion.
Pursuant to another advantageous specific embodiment of the
inventive method, the abrasive is conveyed into the water jet at
essentially right angles to the axis thereof, thus resulting in an
optimum supply of the abrasive to the water jet; in other words the
shortest possible path is provided from the mouth of the abrasive
inlet to the water jet.
It has been shown that in principle the abrasive can be conveyed
into the mixing chamber at any desired pressure. In applications in
a normal atmosphere however, the abrasive is preferably added to
the mixing chamber in a pressure range of 1 bar relative to the
inner pressure of the mixing chamber. However, abrasive pressures
of 1 to 120 bar are also possible.
The inventive apparatus for carrying out this method is
characterized primarily in that the axis of the abrasive inlet in
the mixing chamber extends essentially perpendicular to the axis of
the water jet in the mixing chamber.
The advantage of this novel arrangement is essentially that the
particles of abrasive that are blown in via the abrasive inlet are
conveyed into the water jet along the shortest path, so that the
inventive object of obtaining an optimum feed geometry for the
abrasive is achieved.
In principle, the mixing chamber can have any desired
configuration. However, it has been shown that it is advantageous
for the mixing chamber to have an essentially cylindrical
cross-sectional configuration with the axis of the water jet being
the axis of the cylinder, and with the diameter of the mixing
chamber being greater than the free length of the path of the water
jet through the mixing chamber. Mixing chambers of this type are
relatively easy to produce and, due to their symmetrical
construction, offer in all directions a uniform radial spacing
about the axis of the water jet, so that during start-up, moistened
abrasive that collects about the outlet as intended can pile-up
uniformly.
About the outlet, the mixing chamber preferably has a funnel-shaped
configuration, i.e. has a conical cross-sectional configuration, so
that especially when the discharge nozzle, for the discharge of the
water/abrasive mixture out of the apparatus, preferably projects at
least partially into the mixing chamber, a dead space can form that
is a starting point for the deposition of the moistened abrasive at
the base of the mixing chamber. The discharge nozzle is basically
advantageously disposed in the center of the cylindrical mixing
chamber. However, other configurations are also conceivable where
the discharge nozzle is not disposed concentric to the axis of the
mixing chamber, for example where adjustable centering aids are
provided.
Pursuant to the present invention, it is not absolutely necessary
that the discharge nozzle be made of hard material. Furthermore, in
addition to a one-piece construction, the discharge nozzle can also
advantageously be segmented. However, the discharge nozzle is
advantageously made of a hard metal such as tungsten carbide or the
like. This construction takes into account the fact that with the
inventive apparatus merely the discharge nozzle is subjected to
great stress from the water/abrasive mixture that passes
therethrough, and the preceding mixing chamber is not stressed in
this manner since the moist abrasive mixture is deposited about the
outlet of the mixing chamber. To this extent, the inventive mixing
chamber can be formed of materials that are more economical to
produce than is the hard metal discharge nozzle, with such material
being easy and hence economical to work.
Pursuant to another advantageous specific embodiment of the
inventive apparatus, on that side that faces the mixing chamber the
inlet nozzle has a funnel-shaped configuration, increasing in size
in the direction toward the mixing chamber. This configuration of
the discharge nozzle is advantageous because the water jet that
passes through the mixing chamber widens between the time that it
enters the mixing chamber and the time it leaves the same. Due to
the funnel-shaped configuration of the outlet or discharge nozzle,
the water jet that already contains the abrasive is again brought
together.
Pursuant to a different advantageous specific embodiment of the
present invention, having a similar effect as that previously
described, the discharge nozzle can be provided on that side that
faces the mixing chamber with an inlet bore that enlarges the
nozzle opening. However it should be noted that in neither case is
the funnel-shaped configuration of the opening of the discharge
nozzle that is directed toward the mixing chamber absolutely
necessary in either the funnel-shaped form or in the form of the
cylindrical bore.
Where small water diameter nozzles are used, i.e. where the
hydraulic power is low, such as is advantageously used in order to
achieve thin precision cuts, the expansion of the jet due to the
short free jet length that is possible with the present invention,
is so small that no additional widening of the abrasive nozzle bore
in the inlet region is required.
In order to be able to overall optimize the effectiveness of the
inventive apparatus for each predetermined application, it is
advantageous to select the free jet length of the water jet within
the mixing chamber. To do so, it is advantageous for the distance
(free path length) between the inlet and the outlet of the water
jet in the mixing chamber to be adjustable, with this distance or
spacing advantageously being adjusted by shifting of, for example,
the discharge nozzle in the direction of the axis of the water jet.
For example, the free path lengths of the water jet within the
mixing chamber could be adjusted between 2 and 80 mm. Means for
adjusting the free path length spacing between the first inlet and
the outlet for the water jet in the mixing chamber are provided.
The adjusting means may comprise means for shifting the discharge
nozzle and/or the holder for a nozzle insert at which the first
inlet of the mixing chamber is disposed. The adjusting means may
further comprise means for securing the discharge nozzle and/or the
holder within a mixing chamber body. The securing means, for
example, may be in the form of a set screw engaging the discharge
nozzle and/or the holder for the nozzle insert. Alternatively, a
shoulder may be provided at either the discharge nozzle or the
holder whereby the respective shoulder rests at a corresponding
further shoulder or abutment of the mixing chamber body.
In order to be able to adapt to the selected free path length of
the water jet between the inlet and the outlet of the mixing
chamber, the cross-sectional configuration of the abrasive inlet
could also be variable, with this advantageously being effected by
disposing in the abrasive inlet a sleeve having a suitably selected
throughbore cross section.
For certain applications, instead of having merely one abrasive
inlet, it is advantageous to provide a plurality of abrasive inlets
that are directed toward the mixing chamber and that all have their
axes oriented essentially perpendicular to the axis of the water
jet. Depending upon the application, the abrasive inlets can be
distributed in a suitable manner in the mixing chamber about the
axis of the water jet, and can even be disposed at varying heights
between the inlet and the outlet of the mixing chamber.
Finally, it is advantageous to provide precision cylindrical or
conical fitting elements to achieve a centering of the abrasive
nozzle bore relative to the axis of the water jet.
Further specific features of the present invention will be
described in detail subsequently.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings in detail, the apparatus 10
essentially comprises a mixing chamber body 120 as well as a
so-called connector 121, the free end of which is connected in a
known manner with a pressure line. The connector 121 has a
throughbore that extends essentially centrally therethrough and
through which the stream of water 15 that is supplied via the
non-illustrated pressure line passes. Provided at the bottom end of
the connector 121 that faces the mixing chamber 12 is a nozzle
insert 24 that surrounds, for example, the high pressure water
nozzle means 240 that is made of a hard material such as sapphire
or the like. The nozzle insert 24 has a throughbore that
essentially extends centrally therethrough, with that end of the
throughbore that faces the mixing chamber 12 forming an inlet 13
for the water or water jet 15 into the mixing chamber 12. If it
becomes worn, damaged, or it is desired to change the diameter of
the water jet 15, the nozzle insert 24 can be replaced very
rapidly, because it is retained between the connector 121 and a
holder 122 in a conical centering opening via a threaded connection
between the components 121 and 122.
The mixing chamber body 120 is essentially axially symmetrical, as
can be seen from FIGS. 1 and 5. Provided within the mixing chamber
body 120 is an essentially cylindrical mixing chamber 12 in which,
as will be described in detail subsequently, the abrasive 160 is
blown into the jet of water 15 that passes through the mixing
chamber 12 from the inlet 13 to the outlet 14 thereof.
The bottom end of the mixing chamber 12, which faces the outlet 14,
is tapered in a funnel-like manner in the embodiment of FIG. 1.
However, as shown in the embodiment of FIG. 5, the bottom end of
the mixing chamber 12 could also have a planar configuration.
In the illustrated embodiment, the axis 18 of the jet of water 15
coincides with the axis of the cylindrical mixing chamber 12. At
the bottom end, i.e. in the funnel-shaped portion of the mixing
chamber 12, a discharge nozzle 21 is disposed in the extension of
the axis 18 of the water jet 15. The discharge nozzle 21 is made of
a hard material and has a central throughbore to allow the
water/abrasive mixture 11 to pass through.
In addition, the discharge nozzle 21 can be provided with a
shoulder 26 that can come to rest against a corresponding shoulder
or rib in the mixing chamber body 120 (FIG. 1a, FIG. 5a). By
varying the location of the shoulder 26 for different discharge
nozzles, the entry depth to which the respective discharge nozzle
extends into the mixing chamber 12 may be varied.
The adjustment of the free distance or spacing 20 to a desired
value may also be achieved by shifting the discharge nozzle 21
within the mixing chamber body 120 and securing the selected
position with a respective securing means that engages the
discharge nozzle 21. For example, such a securing means may be in
the form of a setscrew or lock bolt.
Furthermore, relative to the entry depth of the discharge nozzle 21
into the mixing chamber 12, and in relation to the inner diameter
for the through passage of the water/abrasive mixture 11, variously
configured discharge nozzles 21 can be used that can be adapted to
the correspondingly desired cutting or cleaning parameters of the
desired insert. The degree to which the discharge nozzle 21 extends
into the mixing chamber 12 determines the free distance or spacing
20 of the water jet 15 between the inlet 13 and the outlet 14. The
outlet 14, in this embodiment, is formed by the funnel-shaped
configuration 22 of the nozzle opening 23.
As illustrated in FIG. 5, the discharge nozzle could also be
segmented. The advantage of this construction is that it is easier
to produce the precision bore in the hard-material nozzle,
especially where small diameters are involved, due to the shorter
construction of the nozzle parts. Furthermore, it is frequently
only the lower portion 211 of the nozzle that needs to be replaced
when this becomes necessary due to wear of the focusing bore. After
not too great operating times, the upper used nozzle portion 210,
while maintaining the jet parameters, frequently has a suitable
inlet geometry, like a new nozzle, since it is ground by the action
of the preceding abrasive stream.
The axis 17 of the abrasive inlet 16 extends essentially
perpendicular to the axis 18 of the water jet. Sleeves 25 of
various diameters can be selectively inserted and secured in the
abrasive inlet 16. The inner diameters of the sleeves 25 are
selected in conformity to the desired free distance (spacing) 20 in
order to conform the effectiveness of the apparatus 10 to the
desired cleaning or cutting conditions.
The orientation of the abrasive nozzle bore 212 parallel to and
concentrically relative to the water jet axis 18 is advantageously
effected by precise cylindrical and/or conical fitting elements
123, 124, 125, 126. In conjunction with a precisely configured
abrasive nozzle bore 212, a symmetrical supply of a stream to the
abrasive nozzle 21 is achieved, which leads to low focusing losses
and a longer service life of the nozzle 21.
The use of components having greater tolerances, especially for
discharge nozzles 21 that do not have a central discharge nozzle
bore 212, allows the apparatus 10 to be provided with suitable
adjustment possibilities.
Centering of the high pressure nozzle holder 122 via conical means,
see for example the reference numeral 125 in FIG. 5, is
advantageously utilized when it is desired to frequently open and
close the mixing chamber 12, for example to check that possible
scoring of the centering surfaces as a result of entering hard
material particles is reliably prevented.
The use of the conical centering element 125 in conjunction with
the soft-material sealing means 127 additionally permits a
subsequent alignment of the abrasive inlet 16 on any desired
position of the periphery after the apparatus 10 (cutting head) is
installed.
FIG. 6 shows a further embodiment in which the mixing chamber is
provided with two abrasive inlets 16 that are arranged opposite one
another about the circumference of the mixing chamber 12. The
structure of the second abrasive inlet 16' is identical to the
aforementioned inlet 16, having a corresponding sleeve 25' and a
corresponding axis 17'. Thus the axes 17, 17' are oriented
essentially perpendicular to the axis of the water jet 18. Of
course, further abrasive inlets may be distributed about the
circumference of the mixing chamber at certain selected, preferably
equal, distances from one another, for example, three respective
abrasive inlets may be positioned at an angle of 120.degree.
relative to one another or four such abrasive inlets may be spaced
at a 90.degree. angle relative to one another (see FIG. 7). It is
also possible to vary the location of the abrasive inlets relative
to one another with respect to the axial dimension of the mixing
chamber (see FIG. 8).
The operation of the apparatus 10 will be described with the aid of
FIGS. 3 and 4. A water jet 15, which is supplied to the apparatus
in a known manner as described above, passes through the mixing
chamber 12 from the inlet 13 to the outlet 14, whereby the free
distance 20 is suitably adjusted in a predetermined manner. Through
the abrasive inlet 16, abrasive 160 is directly blown in a very
precise manner essentially at right angles to the axis 18 of the
water jet. In so doing, the abrasive 160 is injected into the
mixing chamber 12, for example by air having a pressure of 1 bar
relative to the inner pressure of the mixing chamber.
With special applications, for example, in hyperbaric working
chambers under water, the abrasive can also be supplied at higher
pressures relative to the inner pressure of the mixing chamber 12.
Under this mode of operation, the jet, mixing chamber, and abrasive
supply parameters should be coordinated with one another.
The pressure at which the abrasive is introduced into the mixing
chamber 12 depends on the ambient pressure. For example, when the
device is operated in a remote-controlled manner under water at a
depth of 500 m the abrasive pressure must be in a range of
approximately 50 bar. During manual operation under water at a
depth of 50 m the abrasive pressure must be at 5 bar. Thus,
depending on the application, the abrasive pressure may vary over a
wide range, i.e., from 1 to 120 bar.
Immediately after beginning to blow the abrasive 160 in, which can,
for example, comprise all customary and natural or synthetically
obtained or manufactured materials, such as quartz sand, granite
sand, copper grit, corundum, hard metal particles, or other
suitable solid materials, the abrasive collects around the outlet
14, which in the illustrated embodiment is formed by the discharge
nozzle 21 that projects into the mixing chamber, with this abrasive
piling up and forming, together with a spray water fraction that
naturally occurs in the mixing chamber 12, moistened, piled-up
abrasive 161. At the same time, an abrasive channel 162 forms in
the piled-up abrasive 161 about the outlet 14; the subsequent
abrasive coming from the abrasive inlet 16 is guided by the
abrasive channel 162 into the jet of water 15. As a consequence of
the deposition of the piled-up abrasive 161, the walls of the
mixing chamber 12 are protected from erosion as a result of the
abrasive 160 itself, so that it is even possible to use materials
that are not very resistant to wear to produce the mixing chamber
12, for example such materials that are easy to work with and in
addition are economical to produce.
As a consequence of the geometry of the abrasive channel 162, which
is automatically formed as a function of the free distance 20 of
the water jet 15 and as a function of the pressure of the abrasive
160, a suitable acceleration of the abrasive 160 can be effected.
In other words, the effectiveness of the transfer of energy via the
water jet 15 to the abrasive is optimized and is adapted to the
respectively desired conditions. In so doing, the air jets that
move in the throughbore of the discharge nozzle 21 to the free
nozzle opening are suitable to further increase the transfer of
energy to the abrasive 160. To optimize the quantity of air, the
suitable dimensioning of the opening diameter of the abrasive inlet
and also of the supply line of the abrasive 160 to the apparatus
itself should therefore also be taken into consideration.
Pursuant to the method and apparatus 10 of the present invention,
mixing chambers 12 having the following performance data can be
produced and operated:
______________________________________ Pressure range of the water
jet: approximately 300-6,000 bar Hydraulic power: 0.5-50 kw
Quantity of abrasive: 0.1-10 kg/min Quantity of air: 10-500 l/min
______________________________________
In this connection, the discharge nozzle 21 can have an opening or
passage diameter of 0.5 to 3 mm, with the length of the nozzle 21
being between 10 and 200 mm. The free distance (spacing) 20 can be
between 2 and 80 mm.
The present invention is, of course, in no way restricted to the
specific disclosure of the specification and drawings, but also
encompasses any modifications within the scope of the appended
claims.
* * * * *